There are many medicament delivery devices on the market that can perform a number of functions automatically.
One such medicament delivery device, disclosed in International Publication WO 2005/044348, is capable of a penetration sequence, an injection sequence, and thereafter a withdrawal sequence when a user has activated the device by first pressing it against an injection site and thereafter pressing an actuation button.
The device has been successful and is on the market for a number of different drugs for treatment of different diseases. The device uses a drive spring for both the penetration sequence as well as the subsequent injection sequence. For some drugs, it is desirable that the spring is as weak as possible in order that the sequences shall not be performed too fast and at the same time ensure that the medicament container is properly emptied, i.e., that the stopper is moved to the proximal end position inside the medicament container. Even so, it has been found that the injection sequence preferably should be performed even slower in order not to cause pain and discomfort to the user. There is thus room for improvements of an otherwise well-functioning medicament delivery device.